Conductometric and spectroscopic investigations on the reactions between N-methylthiazolidine-2(3H)-selone (1) and N-methylbenzothiazole-2(3H)-selone (2) with Br2

The formation of the compounds C4H7Br2NSSe (3), (C4H7BrNS)(2)[SeBr6] (4) and C8H7Br2NSSe (5) from the reaction of the title selenium donors (1 and 2) with molecular dibromine in CH2Cl2 and MeCN solutions has been investigated by Se-77 and C-13 NMR: UV-visible spectroscopies and by conductometric measurements. In the conductometric titrations of I or 2 with dibromine: the very low values of conductivity recorded up to the 1 : 1 Br-2/1(2) molar ratio indicate the formation of the non-conducting hypervalent selenium compounds 3 and 5, as confirmed by UV-visible and NMR spectroscopies. Above this ratio, 1 and 2 behave differently; in fact, for both of them the conductivity values increase on increasing the amount of added dibromine, but the values recorded for 1, that are much higher than those for 2, are time-dependent. This indicates a kinetic transformation of 1 that has been shown to lead to the previously characterized 4. (C) 1998 Elsevier Science Ltd. All rights reserved.